1. Field of the Invention
The present invention relates to a laser treatment apparatus to perform treatment by irradiating a treatment laser beam emitted from a laser source to an affected area.
2. Description of Related Art
In general, a laser treatment apparatus to irradiate a treatment laser beam to an affected area includes an optical guiding body such as an optical fiber to guide the treatment beam from an apparatus main body containing a laser source, and an irradiation optical system to irradiate the treatment beam guided by the optical guiding body to the affected area. Further, an apparatus that has an irradiation optical system having a beam splitter that splits a treatment laser beam into transmission (a transmitted beam) and reflection (a reflected beam), and a photo-detector that receives one of the treatment beams split by the beam splitter in order to detect (monitoring) an output of the treatment beam has been proposed.
An optical fiber as an optical guiding body is convenient because it is flexible to some degree. However, when an optical guiding status is changed by moving the optical fiber (e.g., kinked, coiled, etc), a polarization status of a laser beam guided by (or outputted from) the optical fiber is also changed. A general beam splitter that can be manufactured easily has a polarization dependence that reflectances are different in the P- and S-polarized components of a laser beam. Thus, there is a problem that a result of detection (a result of monitoring) by the photo-detector is also changed by a change in the polarization status of the treatment beam.